The present invention relates generally to the prevention of pressure ulcers caused by sitting or lying in the same position for extended periods of time. When a force is applied to an area of a person's skin for an extended period of time, local damage to the skin and its underlying tissues can result. This type of injury—commonly known as a pressure ulcer, a decubitis ulcer, or a bed sore—frequently affects persons who are confined to a therapy bed or a wheelchair. In fact, it is estimated that 85% of spinal cord injured patients that utilize a wheelchair will develop a pressure ulcer during their lifetime. Because pressure ulcers can result in serious infections—often chronic and life threatening—and can require long term nursing care or hospitalization, pressure ulcers are major medical concerns in many contexts.